Ph.D. Dissertation Defense: Dinidu Perera
| November 18, 2022 — By Ben Skopic |
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Our very own Dinidu Perera successfully defended his dissertaion! Now he is Dr. Dinidu Perera!
The title of his dissertation was, “Structure, Formation, and Mechanics of Nanofibrillar Spider Silk.” His defense featured three research thrusts, 1) the exfoliation and self-assembly of Golden Orb Weaver (Trichonephila clavipes) silk, 2) nano-indentation of Recluse (Loxosceles laeta) silk, and 3) Raman vibrational spectroscopy on Recluse silk. All three of these projects work towards the goal of obtaining a more detailed understanding of spider silk so that we will be able to better synthesize it, matching the structure and thus, impressive mechanical properties.
In the exfoliation and self-assembly section, he used a bottom-up and top-down approach to obtain identically structured nanofibrils. On the top-down side, he took naturally spun T. clavipes silk and ultra-sonicated it to completely exfoliate the fiber into 10nm nanofibrils. The bottom-up approach took the un-spun silk dope directly from the spider and spin coated it at conditions similar to the natural spinning process and also got 10nm nanofibrils. From this analysis, he concluded that 10nm nanofibrils are the dominate structural component in spider silk. At the current date of this blog post, this work has been uploaded to a pre-print server and is in the process of being re-submitted for peer-reviewed publication. The pre-print manuscript can be found HERE.
The second major project of Dinidu's dissertation focused on determining the anisotropic properties of Relcuse silk using AFM based nano-indentation. Dinidu suspended the ribbon silk over a hole and used the AFM to conduct force-spectroscopy experiments. He indented three different points that we would expect to behave differently due to the nanofibrillar structure of the spider silk. As expected, the point that loaded the nanofibrils in tensile mode was the stiffest, the point that loaded the nanofibrils perpendicularly to their tensile direction was less stiff, and the center point was the least stiff. These results allowed him to determine the tensile and transverse elastic modulus of the spider silk. Additionally, he was able to determine the breaking strength of the nanofibrils. This was a new technique to determine the anisotropic properties of thin films can be used to any such film and can be instrumental in cancer detection. This work was been published in Small and can be found HERE. The lab was featured in the local news for our success with this publication.
The final section investigated the secondary protein structure of the recluse's silk using Raman vibrational spectroscopies. The premise is that different molecular bonds within the silk will have a signature vibrational resonance. In a previous publication, we determined the resonance frequencies of particular secondary protein structures found within recluse silk. Here, Dinidu took it one step farther to strain the silk fibers while in the Raman instrument to determine how these resonance frequencies would change with the strain. This work was preliminary and we will continue to work towards publishing this data.
After the defense, Hannes Schniepp hosted a great party at his house to celebrate!
